Falling Film Flow and Heat Transfer of Cryogenic Liquid Oxygen on Different Structural Surfaces

Abstract

The accurate prediction of the falling film characteristics of cryogenic liquids is necessary to ensure good evaporation performance, due to their special physical properties. In this study, the film flow and heat transfer characteristics on four different structures were investigated, and the performance of the cryogenic liquid oxygen was compared with other fluids with higher temperatures, which demonstrates the influence of structures and liquid mediums. The VOF model was used to capture the film surface in the simulation model. The results show that for the four structures, liquids with higher kinematic viscosity tend to have greater film thickness, and the sensible heat transfer coefficients are inversely related to the nominal thermal resistance of falling film flow. Both on the smooth plate and the corrugated plate, the film wettability depends on the kinematic viscosity, rather than the dynamic viscosity, and the effect of kinematic viscosity is greater than that of surface tension. Both the local heat transfer coefficient and its fluctuation amplitude decrease gradually along the flow direction on the triangular corrugated plate, and the vortices are easier to produce at the wall troughs when the film viscosity is higher. At the bottom of the horizontal tube, the increases in local film thickness of the liquid oxygen are less than those of the water and the seawater. More liquid tends to accumulate at the bottom of the round tube, while it easily detaches from the film surface of the elliptical tube. For the horizontal tubes, the local heat transfer coefficients decrease rapidly when θ = 0–5°, and increase sharply at θ = 175–180°.